It is proposed to utilize a new in vitro preparation of the lens to study the effects of various drugs, hormones and toxic chemicals on lenticular ion transport and permeability. The lens of toads is set in a glass chamber so that the anterior and posterior surfaces are bathed by separate solutions. Under these conditions a PD, short-circuit current and ion fluxes can be measured. An electrode can also be inserted through the glass wall of the chamber in to the lens so that the electrical parameters (including the resistance) can be measured across each surface, inside to front and inside to back. Translenticular ion fluxes, Na, K and Cl will also be measured using this preparation. The effects of such agents (as listed above) on these electrical properties and ion permeability of the lens will be measured. It is hoped that this will extend our understanding of normal physiological processes that regulate and control the permeability of the lens membranes. The more immediate aim is to identify chemicals that alter the permeability of lens membranes to ions and to elucidate the mechanisms by which they may mediate any changes observed.